Playing from library usb, but usb-drive is not connected?

Hi to more experienced volumio users (I’m new since yesterday…)
I’ve added a usb-ssd-harddrive with some music folders inside, to play music from local storage.
Today I removed the harddrive from usb, but I’m still able to play the songs??
How is this possible?
Are there songs stored in any “buffer”, and if so, how big is this buffer?
Best regards!